Excerpt from The Journal of Comparative Psychology, Vol. 1: Robert M. Yerkes<br><br>The method of investigation of learning and the number of trials given were the same as those adopted with the two previous problems. One trial a day method was used. All rats were 40 days old when fed for the first time on the upper platform. T hey were fed 3 at a time for a period of 20 minutes for two successive days. Approximately 50 rats were used. Oi these, 20 were used for the preliminary investigation of the problem.<br><br>About the Publisher<br><br>Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com<br><br>This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.